Employee Benefit Plans - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Anticipated cash contributions to pension plan in remaining fiscal year		$ 0	$ 0
Estimated liability to withdraw from plan		3,307,000	3,307,000
Estimated liability to withdraw from plan, current		240,000	240,000
Estimated liability to withdraw from plan, noncurrent		3,067,000	3,067,000
Pension and Other Postretirement Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 397,000	1,225,000	3,675,000
Expected return on assets	$ 692,000	$ 1,971,000	$ 5,913,000